1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly, to an apparatus for forming an image by a plurality of image forming means.
2. Description of the Related Art
Apparatuses for obtaining a color image by forming images of different colors on corresponding ones of a plurality of photosensitive drums using a laser beam or LEDs (light-emitting diodes), and transferring these images onto a common recording material conveyed by a transfer belt are known.
Since the thickness of an endless moving member, such as a transfer belt, or the like, for conveying a recording sheet is generally uneven, the surface speed of the belt at a contact point between the belt and a belt driving roller is also uneven. As a result, the conveying speed of the recording material at a transfer position of each image forming unit varies, thereby causing position deviation among images of respective colors.
It is an object of the present invention to solve the above-described problems.
It is another object of the present invention to obtain an excellent image by preventing position deviation among respective images constituting the image when forming the respective images on a recording sheet conveyed by an endless moving member.
It is still another object of the present invention to obtain a very precise image at a high speed.
According to one aspect, the present invention which achieves these objectives relates to an image forming apparatus including a plurality of image forming means, an endless moving member for mounting and carrying a recording material so as to transfer each image formed by a corresponding one of the plurality of image forming means at a transfer position, position detection means for detecting a mounted position of the recording material on the endless moving member, and correction means for correcting an image forming timing of the corresponding one of the plurality of image forming means based on a detection output of the position detection means.
According to another aspect, the present invention which achieves these objectives relates to an image forming apparatus including a plurality of image forming means, an endless moving member for mounting and conveying a recording material so as to transfer each image formed by a corresponding one of the plurality of image forming means at a transfer position, first detection means for detecting a predetermined reference position of the endless moving member, second detection means for detecting the recording material at a conveyance start position, and correction means for correcting an image forming timing of the corresponding one of the plurality of image forming means based on a time period until an output from the second detection means is obtained after an output of the first detection means has been obtained.
According to still another aspect, the present invention which achieves these objectives relates to an image forming apparatus including a plurality of image forming means, an endless moving member for mounting a recording material and conveying the recording material from a first position to a second position so as to transfer each image formed by a corresponding one of the plurality of image forming means onto a recording material at a transfer position, driving means for performing driving for conveying the endless moving member, and detection means for detecting a state of conveyance of the recording material at the first position. A driving position of the endless moving member by the driving means is detected in accordance with a detection output of the detection means, and an image forming timing of the corresponding one of the plurality of image forming means is corrected based on the driving position.
The foregoing and other objects, advantages and features of the present invention will become more apparent from the following detailed description of the preferred embodiment taken in conjunction with the accompanying drawings.